Planar Imaging Versus Gated Blood-Pool SPECT for the Assessment of Ventricular Performance: a Multicenter Study
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Planar Imaging Versus Gated Blood-Pool SPECT for the Assessment of Ventricular Performance: A Multicenter Study Mark W. Groch, E. Gordon DePuey, Allan C. Belzberg, William D. Erwin, Mohammad Kamran, Charles A. Barnett, Robert C. Hendel, Stewart M. Spies, Amjad Ali, and Robert C. Marshall Northwestern University Medical School, Chicago; Rush-Presbyterian-St. Luke’s Medical Center, Chicago; Rush University, Chicago, Illinois; St. Luke’s-Roosevelt Hospital, New York; Columbia University, New York, New York; St. Paul’s Hospital, Vancouver, British Columbia; University of British Columbia, Vancouver, British Columbia, Canada; VA Medical Center, Martinez; University of California-Davis, Davis; and Lawrence Berkeley National Laboratory, Berkeley, California Gated blood-pool SPECT (GBPS), inherently 3-dimensional (3D), Planar equilibrium radionuclide angiography (ERNA) is has the potential to replace planar equilibrium radionuclide angiog- well established and provides a relatively simple and non- raphy (ERNA) for computation of left ventricular ejection fraction invasive method to assess ventricular function and, in par- (LVEF), analysis of regional wall motion (RWM), and analysis of right heart function. The purpose of this study was to compare ticular, left ventricular ejection fraction (LVEF) (1,2). In GBPS and ERNA for the assessment of ventricular function in a any planar projection imaging study, anatomic structures large, multicenter cohort of patients. Methods: One hundred sev- overlap. In planar equilibrium blood-pool imaging, the in- enty-eight patients referred in the usual manner for nuclear medi- ferior wall of the left ventricle is obscured by the right cine studies underwent ERNA followed by GBPS. Each clinical site ventricle in anterior and right anterior oblique (RAO) pro- followed a GBPS acquisition protocol that included 180° rotation, jections, and the left atrium may partially overlap, posteri- a 64 by 64 matrix, and 64 or 32 views using single- or double-head cameras. Transverse GBPS images were reconstructed with a orly, the left ventricle in left anterior oblique (LAO) or best Butterworth filter (cutoff frequency, 0.45–0.55 Nyquist; order, 7), septal views. The partial inclusion of the left atrium in a left and short-axis images were created. All GBPS studies were pro- ventricular region of interest (ROI) has been shown to cessed with a new GBPS program, and LVEF was computed from decrease LVEF, because left atrial counts from the filled left the isolated left ventricular chamber and compared with standard atrium may be present in the left ventricular ROI at ven- ERNA LVEF. Reproducibility of GBPS LVEF was evaluated, and tricular end-systole (3). right ventricular ejection fraction (RVEF) was computed in a subset of patients (n ϭ 33). Using GBPS, RWM and image quality from 3D Tomography has been extensively used in myocardial surface-shaded and volume-rendered cine displays were evalu- perfusion imaging, and recently, calculation of LVEF from ated qualitatively in a subset of patients (n ϭ 30). Results: The gated myocardial perfusion SPECT studies has been widely correlation between GBPS LVEF and planar LVEF was excellent reported (4–6). These methods are adjunctive to the assess- (r ϭ 0.92). Mean LVEF was 62.2% for GBPS and 54.1% for ERNA. ment of coronary artery disease by perfusion imaging using ϭ ϫ The line of linear regression was GBPS LVEF (1.04 ERNA 99mTc agents and 201Tl, providing assessment of ventricular LVEF) ϩ 6.1. Bland–Altman plotting revealed an increasing bias in GBPS LVEF with increasing LVEF (Y ϭ 0.13x ϩ 0.61; r ϭ 0.30; function and wall thickening. However, these methods (us- mean difference ϭ 8.1% Ϯ 7.0%). Interoperator reproducibility of ing only 8 gated frames, precluding the computation of GBPS LVEF was good (r ϭ 0.92). RVEF values averaged 59.8%. ejection and filling parameters) have poor temporal resolu- RWM assessment using 3D cine display was enhanced in 27% of tion and, by and large, use geometric methods to compute the studies, equivalent in 67%, and inferior in 7%. Conclusion: LVEF. These methods do not fare well in the presence of GBPS LVEF was reproducible and correlated well with planar high extracardiac activity or low counting statistics and in ERNA. GBPS LVEF values were somewhat higher than planar patients with severe perfusion defects or small hearts (7–9). ERNA, likely because of the exclusion of the left atrium. Moreover, errors in the assessment of myocardial wall Key Words: gated blood-pool imaging; gated SPECT; left ven- tricular ejection fraction thickening because of the partial-volume effect have been reported (9). J Nucl Med 2001; 42:1773–1779 For analysis of ventricular function, gated blood-pool SPECT (GBPS) has the benefit of the tomographic perspec- tive to isolate the left and right ventricles without overlap of Received May 18, 2001; revision accepted Aug. 7, 2001. other cardiac chambers and to improve the assessment of For correspondence or reprints contact: Mark W. Groch, PhD, Department of Nuclear Medicine, Northwestern Memorial Hospital, 251 E. Huron St., regional wall motion (RWM) (10–16). Further, most re- Chicago, IL 60611. ported GBPS methods are truly volumetric in their compu- PLANAR IMAGING VERSUS GATED BLOOD-POOL SPECT • Groch et al. 1773 tation of LVEF and ventricular volumes. GBPS images can GBPS be acquired in less time than is needed for a 3-view planar Acquisition. GBPS was performed using either a single-head ERNA series using multihead gamma cameras (approxi- gamma camera (42 patients) or a double-head gamma camera in mately 15 min), improving patient throughput. Using GBPS the 90° configuration (136 patients). All patient studies were Ϫ has an added advantage, because the best septal view, unlike acquired using a 180° arc, starting at 45° (RAO), using either a low-energy, all-purpose collimator (single-head systems) or a planar imaging, need not be found for computation of high-resolution collimator. Single-head systems used a circular LVEF. The search for the best septal view is frequently orbit, whereas double-head systems used either circular or noncir- tedious and sometimes unproductive. cular orbits, depending on the institutional protocol. Images were The computation of right ventricular ejection fraction acquired in a 64 by 64 matrix with a zoom of 1.23 or 1.45 (RVEF) with planar ERNA techniques is unreliable at best. (depending on heart size), using either 32 views at 1 min per First-pass techniques have become the standard for compu- projection for single-head systems or 64 views (32 per head) at tation of RVEF but are tedious to perform and can lack 30 s per projection for double-head systems, in step-and-shoot adequate statistics (16). Using GBPS, not only can the effect mode. Conventional ECG gating was used with a wide R-R ac- on LVEF from left atrial activity contamination be re- ceptance window (60%), and 16 forward-gated frames were ac- moved, but also, potentially, RVEF may be accurately quired over the cardiac cycle, using standard on-the-fly arrhythmia rejection. With this protocol, double-head gamma camera acqui- quantified. With improved gamma cameras and faster com- sitions typically contained approximately 30–40 million total puters, GBPS may become a practical tool for assessment of counts (2–2.5 million counts per time bin). GBPS was successfully ventricular performance. However, the calculation of global performed for all patients. LVEF from GBPS has not been evaluated in a large-scale Reconstruction. Transverse 64 by 64 images were reconstructed study. The purpose of this investigation was to compare with a ramp filter using a seventh order, 2-dimensional Butter- GBPS assessment of ventricular performance and, in par- worth filter and a cutoff frequency of 0.45–0.55 Nyquist for each ticular, global LVEF with planar ERNA assessment in a of the 16 time bins. The default cutoff was 0.55 Nyquist. However, multicenter environment and to establish reference limits if the projection data appeared noisy on the cine display because of for RVEF from a cohort of patients with normal right arrhythmias or irregular rhythms, the cutoff was adjusted down- ventricular function. Additionally, the reproducibility of ward to between 0.50 and 0.45 Nyquist. Flood and center-of- rotation corrections were applied, but not attenuation or decay manually determined GBPS LVEF computation was as- correction. Short- and long (sagittal or coronal)-axis oblique slices sessed, and visual assessment of RWM from 3-dimensional were formed by reorienting the transverse image data using stan- (3D) surface-shaded displays was compared with planar dard, partly manual methods. The total reconstruction and process- ERNA cine assessment in a subset of patients. ing time was Ͻ10 min. Analysis of Ventricular Performance MATERIALS AND METHODS A quantitative GBPS program (NUMUGAS; Northwestern Planar and GBPS Studies University, Chicago, IL) was coded using the IDL language (Re- Planar and GBPS studies were successfully acquired for 178 search Systems Inc., Boulder, CO) on an ICON computer (Sie- patients from the 5 participating clinical sites, who were referred in mens Medical Systems, Hoffman Estates, IL). The GBPS program the usual manner for nuclear medicine assessment of ventricular creates a 3D, rotatable, cine display of volume renderings (maxi- function. Both the planar and the GBPS studies were acquired on mum intensity projection [MIP]) and surface-shaded renderings the same day—the SPECT study immediately after the planar from the short-axis oblique dataset. Figure 1 illustrates a typical views. The population was largely composed of chemotherapy surface-shaded and volume-rendered display in 1 long-axis orien- patients (124 patients) and also included some coronary artery or tation. The program quantifies ejection fraction, volumetrically, heart disease patients and 8 heart failure patients. A dose of using maximal or minimal (diastole to systole) count change from 925–1110 MBq 99mTc was administered as a blood-pool tag, with each site using its own tagging protocol.